Invasive species continue to be reported in the municipality. In just the past 15 years, nearly 400 observations have been made, according to the Swedish University of Agricultural Sciences (SLU). A continued increase in these species could affect nature, infrastructure and human health.
Since 2010, 380 observations in Nynäshamn have been reported on Artportalen, a service operated by the Swedish University of Agricultural Sciences (SLU). Among the most common are giant hogweed and Japanese knotweed. Two plants that bring problems for ecosystems and society.
Invasive species have been moved with the help of humans to an area where they have not previously existed. They can then develop into invasive species. This means that the species spread quickly and cause extensive damage to nature, people or the economy.
”If we do not take any action, Japanese knotweed and giant hogweed will definitely increase. We will probably never be able to get rid of either of them completely, but we have to try to stop the spread and mitigate the effects these species have on nature,” says Peter Dalin, an officer at the Swedish Environmental Protection Agency with a background in biology.
Giant hogweed is a tall plant with white flower clusters. It spreads quickly in open areas and along roadsides. Giant hogweed is included in the EU legislation on invasive alien species, which means that it is prohibited to import or otherwise release it into nature. The species can cause serious skin damage upon contact, and it also outcompetes other plants by shading the ground with its large leaves.
Japanese knotweed is currently not included in EU legislation but is considered a high-risk species and should therefore be reported when observed to prevent further spread. Japanese knotweed is a large plant recognised by its bamboo-like, hollow stems and large green leaves. The plant can outcompete all other vegetation in an area by shading large areas of land. It can also cause damage to buildings or roads through its powerful roots.
”As long as there are cracks in the pipes or properties, it can cause problems with its enormous growth. Measures are being taken to combat its spread, but it is very costly and you have to continue for several years.”
Giant hogweed originates from the northern part of the Caucasus mountain range along the border between Russia and Georgia, while Japanese knotweed originates from Asian countries such as Japan, Taiwan and Korea. Unlike native species, there is no natural ecosystem that can keep their populations in check. This makes controlling them more difficult and requires more active measures to prevent their spread.
”Both plants spread at the expense of native plants. Since they have arrived here with the help of humans, they do not have many natural enemies. Nothing eats them, so they are not regulated in the same way as native plants.”
Work against invasive species is ongoing throughout the country, but it is costly and takes a long time. In both the previous year, this year and next year, the Swedish Environmental Protection Agency has received special funding from the government for individual initiatives against invasive species, Dallin explains. He believes that problematic plants such as Japanese knotweed should be covered by legislation, just like the giant hogweed, in order to better combat their spread.
”Japanese knotweed has to be treated very carefully, and it costs an enormous amount to manage. There have been cases where people have had difficulty selling their properties when Japanese knotweed is found, so it is very troublesome. Our proposal is that Japanese knotweed should be covered by legislation, then hopefully we will be able to allocate more resources to work against it.”
Peter Dallin sees the risks of not introducing measures to stop the spread of invasive species such as Japanese knotweed and giant hogweed as serious:
”There will be increased pressure on biodiversity as well as greater problems with properties and infrastructure. Especially if we do not get rid of giant hogweed, children could get burned by these plants. We have to do something about these plants, otherwise they will take over in too many ways.”
